Cooling tower efficiency measures how effectively a tower removes heat from circulating water, expressed as the ratio of actual temperature drop achieved compared to the theoretical maximum possible. Standards like ASHRAE 143 define testing methods at specific conditions, typically 95°F entering water, 78°F wet bulb, and 85°F leaving water. Higher efficiency ratings indicate superior heat rejection capability.
Performance Metrics
Efficiency is calculated as (inlet temperature minus outlet temperature) divided by (inlet temperature minus wet bulb temperature), multiplied by 100. Modern commercial towers achieve efficiencies between 70-90% under design conditions. Efficiency decreases approximately 2-3% for every 5°F increase in wet bulb temperature above design conditions. The Cooling Technology Institute (CTI) provides standardized performance ratings allowing equipment comparison across manufacturers.
Operational Significance
Seasonal efficiency variations affect system performance and energy consumption throughout the year. Winter operation at lower wet bulb temperatures improves efficiency to 95%+, while summer peaks may drop to 60-70% in hot climates. Regular maintenance including water treatment and fill media cleaning prevents efficiency degradation. Poor efficiency indicates fouled tubes, insufficient air flow, or inadequate water distribution requiring corrective action to maintain system cooling capacity.